The invention relates to a device for tensioning and closing strapping bands for packages and suchlike, with a band channel open on one side on a longitudinal side in the longitudinal direction of the band, a band tensioning device acting in the area of the band channel and a closing device which joins the band ends of the strapping bands lying on top of each other in a tensioned state in the band channel.
A device of this type is known, for example, from DE 100 26 197 A1/U.S. Pat. No. 6,957,678 B2. This known device is suitable for closing strapping bands of different widths. In order to do this a band stop is envisaged which laterally guides the band ends of the strapping band in the band channel and delimits the band channel internally, the position of which can be changed perpendicularly to the longitudinal direction of the strapping band. The band channel has, depending on the position of the stop, an appropriately large width for taking up a wide strapping band, and a narrower width for use of the device for a narrow band.
The ability to alter the band channel width with the aid of a laterally adjustable band stop in the known device allows bands of different widths to be easily processed with one and the same device. This, however, results in the problem that not only the bandwidth has to be set by the user by adjusting the stop, but also it becomes necessary to set the band closing parameters for each band to be processed. It is self-evident that a narrow strapping band cannot be tensioned with the same maximum tensioning force as a broad band and the optimum welding time, tensioning rate, holding time after welding or other band closing parameters for a broad band can be completely unsuitable for a narrow band. If a narrow band is processed with the band closing parameters applicable to a broad band, the narrow band and the strapped package can be easily damaged and/or the closure can be inadequate.
In the known device the closing parameters are therefore limited through appropriate programming of the electronic control system of the device to a maximum permissible value which is in general set to processing the band with the maximum width. The closing parameters can be manually regulated by the use of the device with the aid of an appropriate adjusting device, in the form of a potentiometer, for example, and thus be reduced for narrower bands.
Unfortunately it has been shown that due to unfamiliarity or convenience many users always operate the device with the maximum closing parameters values, thereby processing narrow bands with the same tensioning force, tensioning rate, welding time, holding time etc as broad bands and are then amazed and complain about the poor quality of the strapping closure produced in this way.
From DE 198 31 665 A1/U.S. Pat. No. 6,470,941 B1 a method and a device for welding bands of thermoplastic synthetic material are known in which the band ends of a strapping band located in the band channel are welded using a friction welding device. The heat supply required for welding is controlled at the welding point in dependence on the thickness of the bands to be welded to each other and the friction welding device is only switched off when a predetermined specified value is reached/fallen below. In this known device/method too, processing of bands of different widths with one and the same device is not envisaged and the aforementioned problems associated therewith do not occur.
From DE 198 31 665 A1 a method and a device for welding bands of thermoplastic synthetic material are known in which the band ends of a strapping band located in the band channel are welded using a friction welding device. The heat supply required for welding is controlled at the welding point in dependence on the thickness of the bands to be welded to each other and the friction welding device is only switched off when a predetermined specified value is reached/fallen below. In this known device/method too, processing of bands of different widths with one and the same device is not envisaged and the aforementioned problems associated therewith do not occur.